1. Field of the Invention
The invention deals with the field of a radionavigation, and, in particular, relates to systems of personal safety indicating the position of an object on the basis of signals emitted by a satellite radio navigational systemxe2x80x94GPSxe2x80x94and generating emergency message, containing positioning data, in an emergency situation.
2. Description of the Related Art
One of the important applications of a user equipment working on GPS signals is its use in systems of tracking of objects, including in systems of monitoring and in systems of personal safety.
The systems of tracking and monitoring of transport (see, for example, application of Germany (DE) 3501035, Int. Cl. 008 G 1/00, published Jul. 17, 1986 [1], application EPO (EP) 0379198, Int. Cl. 001 S 5/02, 001 S 5/14, published Jul. 25, 1990, [2], application EPO (EP) 0509775, Int. Cl. 001 S 5/14, published Apr. 15, 1992 [3], patent of U.S. Pat. No. 5,319,374, Int. Cl. 001 S 1/24, 001 S 5/02, 001 5 3/02, 004 C 11/02, published Jun. 7, 1994 [4]), in which the vehicle is supplied with the unit for a position-fix on GPS signals and radio communication unit to provide a link with a central station monitoring the position of a vehicle.
The systems are known, in which the location of a vehicles is determined on the basis of GPS signals and the location data are transmitted to a tracking station in case of an emergency situation (see, for example, application of Germany (DE) 3839959, Int. Cl. G08 B 25/00, G08 G 1/123, B60 Q 9/00, H04 Q 7/00, published Apr. 12, 1990, patent of USA (U.S. Pat. No.) 5,355,140, Int. Cl. G01 S 1/08, G01 S 5/02, published Nov. 11, 1994, application PCT (WO) 93/16452, Int. Cl. 008 G 1/123, published Aug. 19, 1993 [7]).
In the above systems of tracking and monitoring vehicles [1-7] for a position-fix the standard receivers of GPS signals equipped with additional units, ensuring a data transmission about position, and also alarm signals to the monitoring station are used. As a rule, in such systems of GPS receivers there are no special requirements on a position-fix in conditions of partial blocking of a GPS signal reception and requirements dealing with miniaturization of the equipment.
On the other hand, unlike the vehicle positioning, the systems of personal safety might add supplementary requirements to GPS receivers operating for a position-fix. First, it deals with the preferential accommodation of the GPS receiver in a body of a radiophone, as for example in a system de-scribed in application EPO (EP) 0528090, Int. Cl. G01 S 5/00, published Feb. 24, 1993 [8]. It results in necessity to miniaturize the GPS receiver and to minimize power consumption. Second, there might be a requirement to provide a position-fix in conditions of interference of GPS signals, for example in operation conditions xe2x80x9cunder foliagexe2x80x9d.
The GPS receiver is known which is supplied with a communication channel for transmission/reception of messages generated in emergency situations (see application PCT (WO) 97/14057, Int. Cl. 001 S 5/14, G01 S 1/04, published Apr. 17, 1997 [9]), thus, solving the problem of object detection under conditions of interference of GPS signals. The receiver described in, is selected as the prototype. The generalized skeleton diagram of the receiver selected as the prototype, is shown in FIG. 1.
The prototype receiver, see FIG. 1, contains connected in series frequency converter 1 of GPS signals, unit 2 of analog-to-digital conversion of signals and channels switch 3. To the first output of the switch 3 are connected unit 4 for storage of samples of values of signals and, connected in series, signal processor 5. To the second output of the switch 3 the unit 6 of conventional correlation processing is connected. A heterodyne input of the radio frequency converter 1 and clock input of the unit 2 analog-to-digital conversions of signals, and also clock input of the unit 4 for storage of samples of values of signals and clock input of the unit 6 for correlation processing are connected to the appropriate outputs of the signal-former 7 for signals of clock and heterodyne frequencies supplied with means for formation of signals of clock and heterodyne frequencies, for example by synthesizers of frequencies.
The base input of the signal-former 7, comprising the base inputs of the appropriate synthesizers of frequencies, is connected to an output of the base generator 8. A control input of the signal-former 7, formed by the inputs of given initially set synthesizers of frequencies, control input of the switch 3, and also inputsxe2x80x94outputs of the data of the signal processor 5 and unit 6 for correlation processing are connected by the appropriate data buses to the navigational processor 9.
The navigational processor 9 is supplied with the unit 10 for storage of the programs and data. The peripheral equipmentxe2x80x94unit 11 for input-outputs of the data and unit 12 for transmission and reception of the messages on communication channel also is connected to the navigational processor 9. The unit 11 is realized, for example, as a controller, keypad, or display and is supplied with the interface connector. The unit 12 is realized as the modem executing, for example, radio-frequency voice communication of the navigational processor 9 with the base station 13. The base station 13 is supplied with means for a signal reception of an alarm and location information of the receiver, and also means for self-formation of the ephemerical data, rough coordinate information on the position of the receiver, data of Doppler shift and means of transmission of these data through a radio channel to unit 12.
The prototype receiverxe2x80x94operates as follows. The GPS signals from an out-put of a receiving antenna go to an input of the radio frequency converter 1, where their conversion to a lower frequency takes place. Also used in this process are the mixers which are included in a structure of the converter 1, working with the heterodyne signals (Fh), coming from appropriate outputs of the signal-former 7. The signal-former 7 synthesizes signals of clock (Fc) and heterodyne (Fh) frequencies, using for this purpose a signal of a base frequency (Fbase), coming from an output of the base generator 8. The initial setting of values of frequencies, generated by synthesizers, is effected by supplying appropriate initialization code from the navigational processor 9.
From an output of the radio frequency converter 1 signals go to an input of the unit 2 intended for analog-to-digital conversions of a signal, where they are converted to a digital kind. The sampling rate at analog-to-digital conversion is determined by a clock signal (Fc), coming from the appropriate output of the signal-former 7.
Later the signals go to an input of the switch 3 used for processing channels, which switching is effected by a control signal generated by the navigational processor 9.
In a usual mode the switch 3 executes hook up of an output of the unit 2 to an input of the unit 6 (correlation processor). The unit 6 together with the navigational processor 9 executes conventional correlation processing of received GPS signals at a 1 msec interval, including searching for signals on the basis of frequency and code, tracking, decoding, extraction of a service information about ephemerises, extraction of the navigational information (determination of radio navigational parameterxe2x80x94RNP). In particular, thus is achieved the determination of a temporal position of peaks of correlation functions of noise signals of visible satellites, which is used further by navigational processor 9 in calculations of position. The correlation processing in the unit 6 is implemented with a clock frequency determined by a clock signal (Fc), coming from an output of the signal-former 7.
The position information goes to the unit 11 (input-outputs of the data), where, for example, it is displayed on the screen.
The position information goes also to the unit 12, which in a communication session with a base station. 13 transmits to a base station the message about position and, in case of an emergency situation, the alarm signal, which is produced by means of the unit 11 and navigational processors 9.
At a base station 13 the formation of the ephemerical data, rough coordinate data of the receiver and data of Doppler shift takes place, independently from the activity of the receiver, which data goes through the communication channel to the unit 12 of the receiver. These data are used in the receiver operation under the adverse conditions of reception e.g. at a bad signal/noise ratio (at blockade of GPS signals).
In the adverse conditions of reception, i.e. at a bad signal/noise ratio, for ex-ample when the receiver is in a zone of blockade of GPS signals, the switch 3 connects an output of the unit 2 to an input of the unit 4 (storage of samples of values of signals).
The switching of the switch 3 is controlled by a signal shaped by the navigational processor 9, for example, by results of unsuccessful searching for signals with use of the unit 6, or on a signal of the operator, coming from the unit 11.
The unit 4 executes buffer storage of samples of values of signals shaped by the unit 2, at an interval of about 1 second. The record of samples in the unit 4 is implemented with a clock frequency determined by a clock signal (Fc), coming from an output of the signal-former 7.
Stored in the unit 4 samples of values of signals are used by the signal processor 5, which executes searches for signals and their correlation processing with the purposes of extraction of the navigational information (RNP). The data about RNP goes to the navigational processor 9, where the position-fix is being effected. Thus, for implementation of searching for signals, extraction of the navigational information and position-fix in the adverse conditions of a GPS signal reception, the signal processor 5 uses the ephemerical data, rough coordinate information on position and Doppler shift obtained by the navigational processor 9 on communication channel from a base station 13.
The position information determined in the navigational processor 9, goes to the unit 11 for indication, and also to the unit 12 for transmission to the base station 13 monitoring the receiver. Together with position information, the base station, if necessary, is provided with the messages on emergency situations, i.e. the alarm signals are transmitted which are shaped by means of the unit 11 and navigational processors 9 and are transmitted through the communication channel to the base station 13 by means of the unit 12.
Thus, prototype receiver provides a capability of detecting position and alarming both under the usual conditions of a GPS signal reception, and in conditions of their blockade.
One of the characteristic features of the prototype receiver, transmitting a message (alarm signals with a locating information) in emergency situations, is the necessity of fast searching for signals both under a usual conditions of a GPS signal reception, and in conditions of their blockade. The prototype receiver achieves this result by using a high-stability generator as the base generator 8, it is understood that the higher the stability of the base generator, the less time, under equal conditions, is required for tracing signals, both under the normal conditions of a GPS signal reception, and in conditions of their blockade.
However, this maintenance of high stability of the base generator is very labor-consuming, requiring application of special means, for example means thermo-stabilization (thermo-compensation). It makes the prototype receiver more complicated and expensive.
The technical problem to be solved by the present invention is to equip the receiver by means, which allow to determine deviation of frequency of the base generator from a nominal value, using for this purpose an external high-stable base sine-wave signal received on a radio channel from a base station.
The achieved result provides capability for developing data about deviation of frequency of the base generator from a nominal value, which then are used at formation of the adjusting data of a carrier frequency in the navigational processor 9 for control of the signal processor 5 and unit 6 correlation processing when searching for signals. It allows to execute fast searching for signals at a position-fix both under normal conditions of a GPS signal reception, and in conditions of their blockade, thus use of simple base generatorsxe2x80x94simple, not compensated chipsxe2x80x94is possible.
The invention provides a receiver of GPS signals with communication channel for message passing about emergency situations containing, in series, radio frequency converter of GPS signals, unit of analog-to-digital conversion of signals and switch of channel processing, to whose first output are connected joined in series, unit of storage of samples of values of signals and signal processor, and to whose second output are connected the unit of correlation processing. Signal processor and unit of correlation processing are connected with the navigational processor, which is supplied with memory unit for storage of the programs and data.
Heterodyne input of the radio frequency converter and clock inputs of the unit of analog-to-digital conversion of signals, of the unit of storage of samples of values of signals and unit of correlation processing are connected to the appropriate outputs of the former of signals of clock and heterodyne frequencies, which is supplied by means for formation of signals of clock and heterodyne frequenciesxe2x80x94synthesizers of frequencies.
The base input of the former of signals of clock and heterodyne frequencies, which is formed by base inputs of the appropriate synthesizers of frequencies, is connected to an output of the base generator.
Control input of the former of signals of clock and heterodyne frequencies formed by inputs of given, initially set synthesizers, and control input of a communicator of processing are connected to the navigational processor, to which also are connected a data input-output unit and unit of transmission and reception of the messages through the communication channel linking the receiver to a base station.
Also added is the unit of determination of deviation of a signal frequency of the base generator from a nominal value. The first input of the unit is connected to an output of the base generator, the second input is connected by a data bus to the appropriate output of the unit of transmission and reception of the messages on communication channel, and outputxe2x80x94is connected to means of data storage about deviation of a signal frequency of the base generator from a nominal value in the memory unit of the navigational processor connected with means of developing data of a carrier frequency in the navigational processor for control of the signal processor and unit of correlation processing by searching for signals.